The present invention relates to a plasma apparatus for the chemical treatment of samples, to an industrial machine having one or more such apparatuses and to a process using said apparatus.
In particular, the apparatus permits the surface treatment, deposition and chemical etching of thick or thin layers over large sample surfaces at speeds at least 10 or 100 times higher than those obtained with the hitherto known deposition and etching procedures.
It is more particularly used in the microelectronics field for the production of integrated circuits and semiconductor lasers, in the integrated optics field and in the solar field for the photovoltaic conversion of light energy. The integrated circuits to which the invention applies are e.g. circuits for the control of liquid crystal flat-faced screens.
In general, the invention applies to all industrial fields requiring the deposition or etching of thick or thin layers, as well as the chemical cleaning of layers or substrates. These layers and substrates can be dielectrics, metals or semiconductors.
At present there are various etching and deposition apparatus types using a plasma. Generally such apparatuses have a superhigh frequency wave source, a tightly sealed treatment enclosure containing a receiver or a support for supporting the sample to be treated, elements for coupling the superhigh frequency source to the treatment enclosure, gas supplies for forming the plasma and means for pumping the treatment enclosure.
Certain deposition and etching apparatuses also have means for creating a magnetic field in the treatment enclosure, which interacts with superhigh frequency waves in order to ionize the different gases used. These apparatuses make use of the electron cyclotron resonance (ECR) effect. Such an apparatus is more particularly described in "Elongated microwave electron cyclotron resonance heating plasma source" by M. Geisler et al, J. Vac. Sci. Technol., A8 (2), March/April 1990, pp 908-915.
The apparatus according to the invention does not use the magnetic field and therefore the ECR effect. Among non-ECR effect apparatuses, there are plasma assisted chemical vapour deposition apparatuses and machines (PECVD). These machines have been developed for the production of active matrix flat-faced screens and generally use a frequency of 13.56 MHz.
These machines suffer from the disadvantage of using low electron density plasmas not making it possible to obtain a total dissociation of the gases. In order to avoid the diffusion of a non-dissociated gas towards the different deposition plasmas, each plasma is isolated in a vacuum chamber dedicated to the deposition to take place. Each vacuum chamber is equipped with a pumping unit making it possible to obtain a vacuum of approximately 10.sup.-4 Pa and which is usually of the turbomolecular type.
These deposition machines are of a complex nature and are very expensive (10 to 20 million French francs).
Moreover, the complexity of such equipment involves regular maintenance, which significantly reduces the machine availability time. Finally, these machines are generally very large and take up large surface areas in white room-type zones, so that their application is limited.
Another known non-ECR effect apparatus is described in EP-A-398 832. Although this treatment apparatus is less cumbersome than PECVD machines, it still suffers from a certain number of disadvantages. In particular, its construction is complex, so that its manufacturing costs are high. Moreover, due in particular to the plasma forming gas injection mode, it does not make it possible to obtain etching or deposition effects on large surfaces (exceeding 1 dm.sup.2) in a homogeneous manner.